Known methods for the production of optically active 2-hydroxy-4-phenylbutyric acid include optical resolution of an ester prepared from racemic 2-hydroxy-4-phenylbutyric acid and l-menthol [cf. D. Biquard, Ann. de. Chimie, 20, 146 (1933)] and chemical synthesis from benzylmagnesium chloride and optically active glycidic acid (cf. Japanese Patent Laid-Open No. 212329/1987). However the former method comprising optical resolution is disadvantageous in that the l-menthol is expensive, while latter method comprising the chemical synthesis is disadvantageous in that optically active serine which is the starting material for the preparation of the optically active glycidic acid is expensive for industrial uses.
There have been reported microbial enzymes capable of asymmetrically reducing a 2-oxocarboxylic acid to thereby give an optically active 2-hydroxy carboxylic acid (cf. Japanese Patent Laid-Open No. 12975/1985, Japanese Patent Publication No. 11591/1986, Japanese Patent Laid-Open No. 100286/1987, Japanese Patent Laid-Open No. 32480/1988 and Japanese Patent Laid-Open No. 32493/1988). However, none of these references discloses a process for the production of optically active 2-hydroxy-4-phenylbutyric acid from 2-oxo-4-phenylbutyric acid. Furthermore, no process for the production of optically active 2-hydroxy-4-phenylbutyric acid from 2-oxo-4-phenylbutyric acid by using a microorganism has been reported so far.